Cover for a manhole

ABSTRACT

A cover ( 3 ) for mounting on a frame structure ( 1 ) associated with a manhole, the frame structure ( 1 ) having side walls defining a central opening there through, the cover ( 3 ) including: a cover member dimensioned to fit the central opening with a bottom surface of the cover member facing towards an interior of the manhole and a top surface ( 9 ) of the cover member facing away from the manhole, the cover member being moveable with respect to the frame structure ( 1 ) between a closed position, whereby the central opening is covered, and an open position, a lock mechanism for releasably locking the cover member in the closed position, the lock mechanism including one or more locking members ( 13 ) engagable with the frame structure ( 1 ) to thereby retain the cover in the closed position and a lock actuator connected to the locking members ( 13 ) for engaging and disengaging each locking member ( 13 ) with the frame structure ( 1 ), the lock actuator being accessible from the top surface of the cover member, the lock mechanism further including a restraining means for preventing actuation of the locking members ( 13 ) by the lock actuator, and a release actuator accessible from the bottom surface of the cover member for overriding the restraining means such that the locking members ( 13 ) can be disengaged from the frame structure ( 1 ) by operation of the release actuator

FIELD OF THE INVENTION

The present invention relates to a cover for a manhole. More particularly the present invention relates to a cover for a manhole in a ground opening.

BACKGROUND OF THE INVENTION

Manholes are used to permit authorized persons to access underground passageways which contain installations such as electrical and communication lines, natural gas lines, water pipes, sewage systems and the like. A manhole cover is usually placed over the entrance to a manhole and seats in a surrounding frame structure located around an edge of the manhole. In most instances a top surface of the surrounding frame structure and cover lie flush with the surrounding ground surface. The frame structure is usually secured to the edge of the manhole with concrete, asphalt, fasteners or the like.

In order to prevent unauthorised persons from easily accessing the underground passageways manhole covers are typically made of thick steel and concrete to ensure that they are extremely heavy, and therefore difficult, for the average person to lift. In most cases the sheer weight of the cover is the only form of protection used to prevent unauthorised access. However, covers are sometimes also secured in place by some form of fastener which is operated via a top surface of the cover exterior of the manhole.

A problem with prior covers is that once they are securely located in a closed positioned anyone remaining within the underground passageways is trapped as they are not able to access and release the fastener, where installed, and subsequently lift and remove the cover from within the manhole. Even if the fastener is in a released position the cover is still very difficult to lift. This problem is exacerbated by the fact that covers are also prone to jamming against the surrounding frame structure due to thermal expansion during hot weather. In addition, dirt and girt can become wedged between the cover and the surrounding frame structure, particularly if the cover has not been opened in a long while.

A further problem with prior covers, particularly those which are not secured in place by some form of fastener, is that immense pressure within an underground passageway due to an explosion, burst water pipe, etc, could be sufficient to inadvertently separate the manhole cover from the surrounding frame structure.

Accordingly, it would be desirable to provide a cover which overcomes or ameliorates at least one of the above mentioned problems with the prior art.

Any discussion of documents, devices, acts or knowledge in this specification is included to explain the context of the invention. It should not be taken as an admission that any of the material formed part of the prior art base or the common general knowledge in the relevant art in Australia or other countries on or before the priority date of the claims herein.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the present invention there is provided a cover for mounting on a frame structure associated with a manhole. The frame structure includes side walls defining a central opening there through. The cover includes a cover member dimensioned to fit the central opening with a bottom surface of the cover member facing towards an interior of the manhole and a top surface of the cover member facing away from the manhole. The cover member is moveable with respect to the frame structure between a closed position, whereby the central opening is covered, and an open position. The cover further includes a lock mechanism for releasably locking the cover member in the closed position. The lock mechanism includes one or more locking members engagable with the frame structure to thereby retain the cover in the closed position, and a lock actuator connected to the locking members for engaging and disengaging each locking member with the frame structure. The lock actuator is accessible from the top surface of the cover member. The lock mechanism further includes restraining means for preventing actuation of the locking members by the lock actuator and a release actuator accessible from the bottom surface of the cover member for overriding the restraining means such that the locking members can be disengaged from the frame structure by actuation of the release actuator.

The cover is preferably pivotally mounted with respect to the frame structure such that the cover is rotatable between the closed position and the open position. A peripheral edge of the cover member is preferably adjacent to the side walls of the frame structure when the cover member is in the closed position.

Preferably, the lock actuator includes a rotatable member pivotally mounted with respect to the bottom surface of the cover member about a first pivot axis. Each locking member can be engaged and disengaged with an associated aperture in the frame structure by angular movement of the rotatable member. The cover is retained in the closed position when each locking member is engaged in an associated aperture. The apertures are located in the side walls of the frame structure.

The release actuator is preferably pivotally mounted to the rotatable member about a second pivot axis and biased towards the bottom surface of the cover member.

The rotatable member preferably includes a capturing means for selectively engaging with the restraining means to thereby prevent angular movement of the rotatable member. The restraining means is preferably a bolt such as a barribolt which is locatable in a restraining aperture which extends through the cover member. The barribolt is preferably engageable with the capturing means and release actuator to thereby prevent angular movement of the rotatable member. The capturing means is preferably a notch or cut-out portion in the rotatable member.

The release actuator can be pivoted about the second pivot axis in a direction away from the bottom surface of the cover member to thereby disengage the release actuator with the bolt and subsequently permit angular movement of the release actuator and rotatable member about the first pivot axis.

The cover further includes at least one seal breaking device for assisting the cover member to move from the closed position when the locking members are disengaged with the frame structure. The seal breaking devices can be mounted on the bottom surface of the cover member and each preferably include a rotatable lug for engaging with the frame structure, and a handle operatively connected to the lug. Preferably, when the cover is in the closed position movement of the handle in a direction away from the bottom surface of the cover member forces the lug into engagement with the frame structure to thereby lever the cover member away from the frame structure.

The cover can further include biasing means, in the form of a spring operatively connected to the frame structure for biasing the cover member to approximately a 45 degree angle with respect to the central opening in the frame structure.

BRIEF DESCRIPTION OF THE DRAWINGS

Further benefits and advantages of the present invention will become apparent from the following description of a preferred embodiment of the invention. The preferred embodiment should not be considered as limiting any of the statements in the previous section. The preferred embodiment will be described with reference to the following figures in which:

FIG. 1 is a perspective view of the cover according to an embodiment of the invention in a partially open position;

FIG. 2 is a view of the top surface of the cover shown in FIG. 1;

FIG. 3 is a view of the underside of the cover shown in FIG. 1 illustrating the locking members in a retracted position;

FIG. 4 is a view of the underside of the cover shown in FIG. 1 illustrating the locking members in an extended position;

FIG. 5 a is a partial cross sectional view of the cover shown in FIG. 1 illustrating the restraining means trapped between the release actuator and the capturing means of the turntable;

FIG. 5 b is a partial cross sectional view of the cover shown in FIG. 1 illustrating the release actuator pivoted about the second pivot axis in a direction away from the bottom surface of the cover member such that the release actuator is not obstructed by the restraining means;

FIG. 5 c is a partial cross sectional view of the cover shown in FIG. 1 illustrating the release actuator and capturing means in front of the restraining means following rotation of the release actuator about the first pivot axis;

FIG. 6 is a partial view of the top surface of the cover shown in FIG. 1 illustrating an end of the drive member of the lock actuator and a keyed lock end of the restraining means according to an embodiment of the invention;

FIG. 7 is a perspective view of a protective cap for covering the apertures in the top surface of the cover shown in FIG. 6;

FIG. 8 a is a partial cross sectional view of the cover and frame structure illustrated in FIG. 1 showing the cover in the closed position with a seal breaking device in a non-operational position;

FIG. 8 b is a partial cross sectional view of the cover and frame structure illustrated in FIG. 1 showing the cover levered away from the frame structure by the lug of the seal breaking device.

DESCRIPTION OF PREFERRED EMBODIMENT

With reference to the accompanying drawings there is shown a cover assembly for a manhole. The cover assembly includes a frame structure I having side walls defining a central opening therethrough. The frame structure 1 being attachable to the manhole. The cover assembly further includes a cover 3 pivotally mounted with respect to the frame structure 1 such that the cover 3 is rotatable between a closed and fully open position. The cover 3 includes a cover member, which is preferably in the form of a cover panel 5, that is planar and dimensioned to fit within the central opening with a bottom surface 7 of the cover panel 5 facing towards the interior of the manhole. The cover panel 5 further includes a top surface 9 which faces away from the manhole. A peripheral edge 11 of the cover panel 5 is adjacent to the side walls of the frame structure 1 when the cover 3 is in a closed position. When the cover assembly is installed over a manhole the top surface 9 of the cover panel 5 preferably lies flush with the ground surface surrounding the manhole.

The cover 3 further includes a lock mechanism for releasably locking the cover 3 in the closed position. In this regard, the lock mechanism includes one or more locking members 13 which are each preferably in the form of a metal rod. The lock mechanism further includes a lock actuator for moving the locking members 13 into and out of engagement in their associated aperture in the frame structure 1. The lock actuator includes a rotatable member, which is preferably in the form of a turntable 15, that is connected to an end of each locking member 13. The lock actuator further includes a drive member 17 connected to the turntable 15. The drive member 17 of the lock actuator extends through a drive aperture 18 in the cover panel 5 such that the lock actuator is accessible from the top surface 9 of the cover panel 5. The drive member 17 is fixed to the turntable 15 such that rotation of the drive member 17 imparts rotational movement to the turntable 15 about a first pivot axis 20 which corresponds with a longitudinal axis of the drive member 17. In turn, rotation of the turntable 15 causes each locking member 13 to move between an extended position, as shown in FIG. 4 and a retracted position as shown in FIG. 3. When the cover 3 is in the closed position, and the locking members 13 are in the extended position, the locking members 13 are engaged in their associated apertures in the frame structure 1. Whereas, when the locking members 13 are in the retracted position, they are disengaged with the apertures in the frame structure 1.

As shown in FIG. 6 the drive member 17 of the lock actuator extends through the drive aperture 18 in the cover panel 5. In a particularly preferred embodiment the drive member 17 is in the form of a bolt having an hexagonal head which can be rotated with an appropriate tool to thereby rotate the drive member 17.

In order to prevent the lock actuator from readily being rotated the lock mechanism further includes a restraining means 19 for preventing actuation of the locking members 13 by the lock actuator. The restraining means 19 extends through a restraining aperture 21 in the cover panel 5 such that the restraining means 19 can be operated from the top surface 9 of the cover panel 5. The restraining means 19 extends through the restraining aperture 21 in the cover panel 5 into engagement with the turntable 15. In this regard, the turntable 15 includes a capturing means for engaging with the restraining means 19 to thereby prevent angular movement of the turntable 15 in one direction. The capturing means is preferably in the form of a notch or cut-out portion 23 in a side edge of the turntable 15.

The lock mechanism further includes a release actuator 25 which is pivotally mounted to the turntable 15 about a second pivot axis 27 which lies perpendicular to the longitudinal axis of the drive member 17. The release actuator 27 is biased towards the turntable 15 and the bottom surface 7 of the cover panel 5. The restraining means 19 prevents rotation of the turntable 15 in a clockwise and anti-clockwise direction by engaging with both the cut-out portion 23 of the turntable 15 and the release actuator 25. In FIGS. 3 and 4 the restraining means 19 is not shown. However, when the restraining means 19 is located in the restraining aperture 21 the turntable 15 will be prevented from moving in a clockwise or first direction due to the engagement of the restraining means 19 with the cut-out portion 23. Similarly, an attempt to move the turntable 15 in an anti-clockwise or second direction will result in the restraining means 19 engaging with the release actuator 25.

The release actuator 25 can be pivoted about the second pivot axis 27 in a direction away from the bottom surface 7 of the cover panel 5. In FIG. 5 a, the restraining means 19 is shown positioned between the notch 23 of the turntable 15 and the release actuator 25. In this position, the turntable 15 and release actuator 25 are not able to be rotated about the first pivot axis 20. In FIG. 5 b, the release actuator 25 is shown in a position whereby the release actuator 25 has been pivoted about the second pivot axis 27 away from the bottom surface 7 of the cover panel 5 such that the release actuator 25 is clear of an end of the restraining means 19. When the release actuator 25 is in this position it is then possible to rotate the release actuator 25 and the turntable 15 attached thereto about the first pivot axis 20 to thereby selectively extend and retract the locking members 13. In FIGS. 3 and 5 c, the release actuator 25 and the notch 23 in the turntable 15 are both shown in front of the restraining means 19 following rotation of the release actuator 25 about the second pivot axis 27 and then the first pivot axis 20. Accordingly, even if the restraining means 19 is in the restraining aperture 21, as shown in FIGS. 5 a, 5 b and 5 c, the locking members 13 can still be moved between an extended and retracted position by operation of the release actuator 25 in the above described manner.

With reference to FIGS. 8 a and 8 b the cover 3 further includes a one or more seal breaking devices 29 for assisting the cover 3 to move away from the closed position when the locking members 13 are in the retracted position and thereby disengaged with the frame structure 1. The seal breaking devices 29 can be located at various locations around the peripheral edge 11 of the cover panel 5 on the bottom surface 7 of the cover panel 5. Each seal breaking device 29 includes a rotatable lug 31 and a handle 33 operably connected to the rotatable lug 31. As can be seen in FIG. 8 a, when the cover 3 is in a closed position the rotatable lug 31 of the seal breaking device 29 is in a position such that is does not inhibit the cover 3 from being in a fully closed position. By moving the handle 33 of the seal breaking device 9 in a direction away from the bottom surface 7 of the cover panel 5, as shown in FIG. 8 b, the rotatable lug 31 is rotated downwardly into engagement with the frame structure 1 to thereby lever the cover 3 away from the frame structure 1.

The cover 3 may further include a biasing means in the form of a spring 37, as shown in FIGS. 3 and 4, operatively connected to the frame structure 1. The spring 37 biases the cover panel 5 to a partially open position, as shown in FIG. 1, whereby the cover panel 5 is approximately at a 45 degree angle with respect to the central opening in the frame structure 1. The cover panel 5 can then be manually pushed to a fully open position such that the cover panel 5 is approximately at a 90 degree or more angle with respect to the central opening in the frame structure 1. The cover 3 further includes a lift arm 39 which operatively connects the cover panel 5 to the spring 37. The lift arm 39 includes a grab handle 41 which can be grasped when opening and closing the cover 3.

In order to open the cover 3 from the exterior of the manhole it is necessary to firstly remove the protective caps 43 in the top surface 9 of the cover panel 5 which protect the ends of the drive member 17 and the restraining means 19. In FIG. 6 it can be seen that the restraining means 19 includes a keyed lock 35 which is operated to release the restraining means 19 from the restraining aperture 21. Alternatively, the restraining means 19 could instead be in the form of a bolt such as a barribolt which is threaded into the restraining aperture 21 and is removable by the insertion of a suitable tool into the restraining aperture 21 to thereby enable rotation of the bolt and subsequent removal from the restraining aperture 21. Once the restraining means 19 has been removed from the restraining aperture 21 the turntable 15 is then free to rotate upon rotation of the drive member 17. In this regard, a suitable tool is inserted over the end of the drive member 17 which is exposed through the top surface 9 of the cover panel 5. As the drive member 17 is rotated in the appropriate direction the locking members 13 will retract and accordingly disengage with the frame structure thereby releasing the lock members 13 from the frame structure 1. Due to the cover 3 being provided with biasing means the cover 3 may without assistance move to a partially open position whereby the cover panel 5 is at an angle of approximately 45 degrees with respect to the central opening in the frame structure 1. However, if the cover 3 has not been opened for some considerable time dirt and grit may have become wedged between the peripheral edge 11 of the cover panel 5 and the frame structure 1 thereby jamming the cover 3 in the closed position. Should this occur the cover 3 can be manually lifted and forced out of the closed position. In this regard, the top surface 9 of the cover panel 5 can be provided with a threaded bore 43 into which a tool may be threaded. The tool can then be forcefully pulled until the cover panel 5 is freed.

In order to close the cover 3 from the exterior of the manhole it is necessary to firstly force the cover panel 5 into the closed position against the biasing force created by the spring 37. Once the cover 3 is in the closed position the exposed end of the drive member 17 can then be rotated with the appropriate tool such that the locking members 13 thereby move to an extended position whereby engagement with the frame structure 1 occurs. In order to prevent unauthorised persons opening the cover 3 it is necessary to then insert and secure the restraining means 19 into the restraining aperture 21. As mentioned previously, an end of the restraining means 19 either includes a keyed lock 35 or a suitably shaped bolt end which can only be rotated with a specific tool which only authorised personnel have access to. Once the restraining means 19 is securely located in the restraining aperture 21 the cover 3 is securely locked in the closed position. The protective caps 43 can then be put in place over the apertures 18, 21 and 43.

In the event that the cover 3 has been securely locked in the closed position with one or more persons inadvertently left within the manhole the cover 3 can still be opened from the interior of the manhole. In order to open the cover 3 from the interior of the manhole the release actuator 25 is pulled away from the bottom surface 7 of the cover panel 5 such that the release actuator 25 pivots about the second pivot axis 27. In this regard, the release actuator 25 is pivoted away from the bottom surface 7 of the cover panel 5 such that the release actuator 25 is sufficiently clear of the restraining means 19 such that the release actuator 19 can be rotated about the first pivot axis 20 over the end of the restraining means 19. Accordingly, the locking members 13 are moved to the retracted position thereby disengaging with the frame structure 1. Should the cover 3 remain jammed against the surrounding frame structure 1 due to thermal expansion during hot weather and/or dirt and grit becoming wedged between the cover 3 and the surrounding frame structure 1, the seal breaking devices 29 can be activated. In this regard, the handles 33 of each seal breaking device 29 is positioned such that operation of the seal breaking devices 29 occurs by pulling the handles 33 away from the bottom surface 7 of the cover panel 5. Accordingly, a trapped individual in the manhole can grasp the handles 33 and use their body weight, if necessary, to rotate the handles 33 such that the rotatable lugs 31 lever the cover panel 5 away from the frame structure 1. Once the cover 3 is no longer jammed against the surrounding frame structure 1 the cover 3 will automatically partially open to approximately 45 degrees with respect to the central opening in the frame structure 1 thereby enabling a trapped individual to escape from the manhole. In this regard, the individual can use the grab handle 41 to lift the cover panel 5 to a fully open position whereby the cover panel 5 is an at angle of approximately 90 degrees or more with respect to the frame structure 1.

The present invention advantageously provides a secure access cover for a manhole whilst at the same time enabling individuals trapped in an underground passage to open the cover in emergency situations.

As the present invention may be embodied in several forms without departing from the essential characteristics of the invention, it should be understood that the above described embodiment should not be considered to limit the present invention but rather should be construed broadly. Various modifications and equivalent arrangements are intended to be included within the spirit and scope of the invention. For example, if a manhole already has an existing cover and surrounding frame structure the cover 3 can be used as a replacement. In this regard, the cover 3 would be suitably dimensioned to the appropriate size for seating in the existing surrounding frame structure located around the edge of the manhole. 

1. A cover for mounting on a frame structure associated with a manhole, the frame structure having side walls defining a central opening there through, the cover including: a cover member dimensioned to fit the central opening with a bottom surface of the cover member facing towards an interior of the manhole and a top surface of the cover member facing away from the manhole, the cover member being moveable with respect to the frame structure between a closed position, whereby the central opening is covered, and an open position, a lock mechanism for releasably locking the cover member in the closed position, the lock mechanism including one or more locking members engagable with the frame structure to thereby retain the cover in the closed position and a lock actuator connected to the locking members for engaging and disengaging each locking member with the frame structure, the lock actuator being accessible from the top surface of the cover member, the lock mechanism further including a restraining means for preventing actuation of the locking members by the lock actuator, and a release actuator accessible from the bottom surface of the cover member for overriding the restraining means such that the locking members can be disengaged from the frame structure by operation of the release actuator.
 2. A cover as claimed in claim 1 wherein the lock actuator includes a rotatable member pivotally mounted with respect to the bottom surface of the cover member about a first pivot axis.
 3. A cover as claimed in claim 2 wherein the rotatable member includes a capturing means for selectively engaging with the restraining means to thereby prevent angular movement of the rotatable member.
 4. A cover as claimed in claim 3 wherein the capturing means is a notch in the rotatable member.
 5. A cover as claimed in claim 4 wherein the restraining means is locatable in a restraining aperture which extends through the cover.
 6. A cover as claimed in claim 5 wherein the restraining means is engageable with the notch in the rotatable member to thereby prevent angular movement of the rotatable member in a first direction.
 7. A cover as claimed in claim 6 wherein the restraining means is engageable with release actuator to thereby prevent angular movement of the rotatable member in a second direction.
 8. A cover as claimed in claim 2 wherein the release actuator is pivotally mounted to the rotatable member about a second pivot axis which lies perpendicular to the first pivot axis.
 9. A cover as claimed in claim 8 wherein the release actuator can be pivoted about the second pivot axis in a direction away from the bottom surface of the cover member to thereby enable disengagement with the restraining member.
 10. A cover as claimed in claim 9 wherein the release actuator can be pivoted about the first pivot axis when disengaged with the restraining member.
 11. A cover as claimed in any one of the preceding claims further including at least one seal breaking device for moving the cover member from the closed position when the locking members are disengaged from the frame structure.
 12. A cover as claimed in claim 11 wherein the seal breaking device includes a lug for engaging with the frame structure, and a handle operatively connected to the lug.
 13. A cover as claimed in claim 12 wherein when the cover is in the closed position, movement of the handle in a direction away from the bottom surface of the cover member forces the lug into abutment with the frame structure to thereby lever the cover member away from the frame structure.
 14. A cover assembly for a manhole, the cover assembly including: a frame structure having side walls defining a central opening there through, the frame structure being attachable to the manhole; and a cover as claimed in any one of the preceding claims, the cover being pivotally mounted with respect to the frame structure such that the cover is moveable between the closed position and the open position. 